1. Field of the Invention
The present invention relates to a backlight chassis for housing a tubular lamp that is a light source of a display device with a backlight, and specifically relates to a backlight chassis preferably used in a liquid crystal display device including a translucent liquid crystal display panel.
2. Description of the Related Art
A liquid crystal display device including a translucent liquid crystal display panel and the like, which are cited as an example of a flat-screen display device, generally have a backlight unit arranged behind the liquid crystal display panel. The backlight unit is a device including a tubular lamp such as a cold cathode tube as a light source, which controls the properties of light emitted from the tubular lamp and projects the light toward a rear side of the display panel. The projected light passes through the display panel, making an image displayed visible on a front side of the display panel.
FIG. 3 is an exploded perspective view schematically illustrating relevant parts of a structure of a generally conventional liquid crystal display device. A liquid crystal display device 30 includes a bezel 31, a display panel 32 and a backlight unit 33. The bezel 31 is a member that defines a frame of the display panel 32, and the display panel 32 is made by bonding two panes of glass to seal in a liquid crystal therebetween.
The backlight unit 33 includes a frame 34, optical sheets 35, tubular lamps 36, a reflector 37 and a backlight chassis 38. The frame 34 is shaped like a picture frame and secures the optical sheets 35 to the backlight chassis 38. The optical sheets 35 are for controlling the properties of light which enters the display panel 32 from the tubular lamps 36. In this case, the tubular lamps 36 are U-shaped, and left-side ends thereof are inserted into electrode part holders 39 so as to be secured to the backlight chassis 38 at the left-end positions, as shown in a plan view of FIG. 4. The reflector 37 is laid under the tubular lamps 36, for reflecting the light emitted from the tubular lamps 36 toward the display panel 32. In order to improve reflectivity, projections 37a in a crest shape are provided on the reflector 37 so as to be located respectively between tube sections 36a of the tubular lamps 36.
The backlight chassis 38, which is prepared by subjecting a metal plate material to plate metal processing so as to have a substantially square shape, includes a lamp housing portion 38a configured by a bottom portion and side-wall portions, and support portions 38b extending outward from the side-wall portions. The frame 34 is secured to the support portions 38b while interposing the optical sheets 35 and the reflector 37.
The tubular lamps 36 are secured to the lamp housing portion 38a of the backlight chassis 38 with the use of the above-mentioned electrode part holders 39 and also with the use of lamp clips 40 for holding the tube sections 36a at an approximate midpoint thereof as illustrated, and the lamp clips 40 are provided in pairs on a coupling plate 41 which is arranged to straddle the projection 37a of the reflector 37. In addition, on a crest portion 41a in the middle of the coupling plate 41, a sheet holding pin 42 is provided. The sheet holding pin 42 is used for preventing the optical sheets 35 which are arranged above from bending downward to preclude luminance irregularity, and has a length so as to leave a predetermined space between the optical sheets 35 and the reflector 37. The lamp clips 40 and the sheet holding pin 42 are molded via the coupling plate 41 in one piece of resin.
A member 43 including the lamp clips 40 and the sheet holding pin 42 is secured to the backlight chassis 38 by making insertion and engagement of protrusions 41b which are provided beneath the coupling plate 41 into and with engaging holes 44 which are punched to be formed both in the reflector 37 and the lamp housing portion 38a, as shown in a detailed drawing in a circle in FIG. 3.
Incidentally, as a prior art literature relating to the present invention, Japanese Patent Application Unexamined Publication No. 2001-210126 is cited.
When using a liquid crystal television receiver or the like, which is cited as a specific example of the liquid crystal display device 30 incorporating the backlight unit 33 in the case of including a loudspeaker system such a speaker, vibrations generated by the loudspeaker system propagate to the backlight unit 33 to sometimes vibrate not only the backlight unit 33 but also the tubular lamps 36 housed therein. At the time of such vibration, if there is looseness of the securing by the engagement of the member 43 including the lamp clips 40 and the sheet holding pin 42 with the backlight chassis 38, a problem of causing an unusual noise such as a fluttering sound arises. However, removing such looseness is difficult in view of manufacturing tolerances and the like of the members, and causes an increase in cost.
In addition, if the backlight unit 33 vibrates at a specific vibration frequency, the vibrations of the tubular lamps 36 and the vibrations of the backlight chassis 38 produce resonance to increase amplitude of the tube sections 36a on the right sides of the lamp clips 40 shown in FIG. 4, and there is a case where U-shaped sections 36b contact the reflector 37 or the like to make a contact noise, or to break the tubular lamps 36. These problems can be solved by placing the members 43 including the lamp clips 40 and the sheet holding pin 42 in vicinities of the U-shaped sections 36b; however, since the optical sheets 35 bend downward more at a center portion 35a, it is not preferable to move the sheet holding pins 42 toward the U-shaped sections 36b. 
As a countermeasure against the above-described problems, instead of the configuration in which the lamp clips 40 and the sheet holding pin 42 are formed in one piece to constitute the member 43, another configuration is possible in which the lamp clips 40 and the sheet holding pin 42 are formed in separate pieces, which are placed in their desired positions, respectively. However, such a configuration increases the number of components as well as the number of securing positions by engagement with the backlight chassis 38, resulting in an increase in positions producing an unusual noise such as a fluttering sound as described above.